Daniel Ferris

Daniel Ferris
University of Florida | UF · Department of Biomedical Engineering

PhD

About

167
Publications
93,539
Reads
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11,244
Citations
Introduction
I am a professor at the University of Florida in the J. Crayton Pruitt Family Department of Biomedical Engineering. I study the biomechanics, neural control, and energetics of human locomotion, with specific regard to robotic exoskeletons, bionic prostheses, and mobile brain imaging.
Additional affiliations
June 2017 - present
University of Florida
Position
  • Professor
August 2001 - May 2017
University of Michigan
Position
  • Professor
May 2000 - August 2001
University of Washington Seattle
Position
  • PostDoc Position
Education
September 1994 - June 1998
University of California, Berkeley
Field of study
  • Human Biodynamics

Publications

Publications (167)
Article
The ability to adapt to environmental and task demands while walking is critical to independent mobility outside the home and this ability wanes with age. Such adaptability requires individuals to acutely change their walking speed. Regardless of age, changes between walking speeds are common in daily life, and are a frequent type of walking adapta...
Article
Full-text available
Improving dynamic balance can prevent falls in humans with neurological and mechanical deficits. Dynamic balance requires the neural integration of multisensory information to constantly assess the state of body mechanics. Prior research found that intermittent visual rotations improved balance training during walking on a narrow beam, but limitati...
Preprint
We developed a method for altering terrain unevenness on a treadmill to study gait kinematics. We attached rigid polyurethane disks (12.7 cm diameter, 1.3-3.8 cm tall) to the treadmill belt using hook-and-loop fasteners. We tested four terrain conditions: Flat, Low, Medium, and High. The main objective was to test the hypothesis that increasing the...
Preprint
Full-text available
Data recordings are often corrupted by noise, and it can be difficult to isolate clean data of interest. For example, mobile electroencephalography is commonly corrupted by motion artifact, which limits its use in real-world settings. Here, we describe a novel noise-canceling algorithm that uses canonical correlation analysis to find and remove sub...
Chapter
Engineers and scientists have long tried to build powered robotic lower limb exoskeletons without success (at least commercially). A major limitation has been the need for large amounts of mechanical power from the actuators. Simply put, human muscles are amazing motors. The size and mass of robotic actuators that can match human muscle limit exosk...
Article
Advances in Mobile Brain/Body Imaging (MoBI) technology allows for real-time measurements of human brain dynamics during every day, natural, real-life situations. This special issue Time to Move brings together a collection of experimental papers, targeted reviews and opinion articles that lay out the latest MoBI findings. A wide range of topics ac...
Article
Full-text available
Active balance control is critical for performing many of our everyday activities. Our nervous systems rely on multiple sensory inputs to inform cortical processing, leading to coordinated muscle actions that maintain balance. However, such cortical processing can be challenging to record during mobile balance tasks due to limitations in noninvasiv...
Article
Full-text available
Reducing the mechanical load on the human body through simulated reduced gravity can reveal important insight into locomotion biomechanics. The purpose of this study was to quantify the effects of simulated reduced gravity on muscle activation levels and lower limb biomechanics across a range of overground walking speeds. Our overall hypothesis was...
Article
Advanced robotic lower limb prostheses are mainly controlled autonomously. Although the existing control can assist cyclic motion in locomotion of amputee users, the function of these modern devices is still limited due to the lack of neuromuscular control (i.e., control based on human efferent neural signals from the central nervous system to peri...
Article
Full-text available
Sustained voluntary muscle contractions can lead to fatigue, which diminishes the muscle's ability to absorb energy and produce force at a desired level. Prolonged fatigue can lead to a decline in human performance and increase the muscle's susceptibility to injury. In this study, we investigated how localized muscle fatigue affected spatial EMG pa...
Article
Full-text available
The spatial distribution of myoelectric activity within lower limb muscles is often nonuniform and can change during different stationary tasks. Recent studies using high-density electromyography (EMG) have suggested that spatial muscle activity may also differ among muscles during locomotion, but contrasting electrode array sizes and experimental...
Article
This special issue highlights some of the best work presented at the 4th International Symposium on Wearable Robotics (WeRob2018), held October 16–20, 2018, in Pisa, Italy. The papers focus on new technologies in the areas of neural interfaces, soft wearable robots, sensor and actuator technologies, and robotic exoskeletons. Based on the quality an...
Poster
Full-text available
Effects of uneven terrain on the stride time and variability of older adults.
Article
Walking with bodyweight support is a vital tool for both gait rehabilitation and biomechanics research. There are few commercially available bodyweight support systems for overground walking that are able to provide a near constant lifting force of more than 50% bodyweight. The devices that do exist are expensive and are not often used outside of r...
Article
On July 1, 2020, the IEEE Transactions on Neural Systems and Rehabilitation Engineering (TNSRE) will be entirely Open Access.We are making this change in response to a growing consensus among our authors and readers—as well as research funders worldwide—that research results should be freely available to the entire scientific community, regardless...
Preprint
Full-text available
Human walking on uneven terrain is energetically more expensive than on flat, even ground. This is in part due to increases in, and redistribution of positive work among lower limb joints. To improve understanding of the mechanical adaptations, we performed analytical and computational analyses of simple mechanical models walking over uneven terrai...
Article
Full-text available
Motion and muscle artifacts can undermine signal quality in electroencephalography (EEG) recordings during locomotion. We evaluated approaches for recovering ground-truth artificial brain signals from noisy EEG recordings. We built an electrical head phantom that broadcast four brain and four muscle sources. Head movements were generated by a robot...
Article
Full-text available
Objective: High-density electromyography (EMG) is useful for studying changes in myoelectrical activity within a muscle during human movement but is prone to motion artifacts during locomotion. We compared canonical correlation analysis and principal component analysis methods for signal decomposition and component filtering with a traditional EMG...
Article
Full-text available
Age-related brain changes likely contribute to mobility impairments, but the specific mechanisms are poorly understood. Current brain measurement approaches (e.g., functional magnetic resonance imaging (fMRI), functional near infrared spectroscopy (fNIRS), PET) are limited by inability to measure activity from the whole brain during walking. The Mi...
Article
Full-text available
Electromyography signal processing approaches have traditionally been validated through computer simulations. Electromyography electrodes and systems are often not validated or have been validated on human subjects where there is no clear ground truth signal for comparison. We sought to develop a physical limb phantom for validation of electromyogr...
Article
The authors tested 4 young healthy subjects walking with a powered knee exoskeleton to determine if it could reduce the metabolic cost of locomotion. Subjects walked with a backpack loaded and unloaded, on a treadmill with inclinations of 0° and 15°, and outdoors with varied natural terrain. Participants walked at a self-selected speed (average 1.0...
Article
Full-text available
Understanding how brain dynamics change with dual cognitive and motor tasks can improve our knowledge of human neurophysiology. The primary goals of this study were to: (1) assess the feasibility of extracting electrocortical signals from scalp EEG while performing sustained, physically demanding dual-task walking and (2) test hypotheses about how...
Article
Full-text available
Objective: Our aim was to determine if walking speed affected human sensorimotor electrocortical dynamics using mobile high-density electroencephalography (EEG). Methods: To overcome limitations associated with motion and muscle artifact contamination in EEG recordings, we compared solutions for artifact removal using novel dual layer EEG electr...
Article
Full-text available
Maintaining balance is a complex process requiring multisensory processing and coordinated muscle activation. Previous studies have indicated that the cortex is directly involved in balance control, but less information is known about cortical flow of signals for balance. We studied source-localized electrocortical effective connectivity dynamics o...
Article
Full-text available
To better understand human brain dynamics during visually guided locomotion, we developed a method of removing motion artifacts from mobile electroencephalography (EEG) and studied human subjects walking and running over obstacles on a treadmill. We constructed a novel dual-layer EEG electrode system to isolate electrocortical signals, and then val...
Article
The coherent spatiotemporal dynamical interplay among neurons, neuronal populations, cortical circuits, and networks cross the micro-, meso- and macro-scales of the human brain, providing the functional organization of the brain and supporting our daily life. The details of how these multiple scales of organization in the brain influence one anothe...
Article
Body-in-the-loop optimization algorithms have the capability to automatically tune the parameters of robotic prostheses and exoskeletons to minimize the metabolic energy expenditure of the user. However, current body-in-the-loop algorithms rely on indirect calorimetry to obtain measurements of energy cost, which are noisy, sparsely sampled, time-de...
Article
Full-text available
Objective: Due to its high temporal resolution, electroencephalography (EEG) has become a promising tool for quantifying cortical dynamics and effective connectivity in a mobile setting. While many connectivity estimators are available, the efficacy of these measures has not been rigorously validated in real-world scenarios. The goal of this study...
Article
Full-text available
Human balance is a complex process in healthy adults, requiring precisely timed coordination among sensory information, cognitive processing, and motor control. It has been difficult to quantify brain dynamics during human balance control due to limitations in brain-imaging modalities. The goal of this study was to determine whether by using high-d...
Article
Objective: Our purpose was to evaluate the ability of a dual electrode approach to remove motion artifact from electroencephalography (EEG) measurements. Approach: We used a phantom human head model and robotic motion platform to induce motion while collecting scalp EEG. We assembled a dual electrode array capturing a) artificial neural signals...
Article
Immersive virtual reality can expose humans to novel training and sensory environments, but motor training with virtual reality has not been able to improve motor performance as much as motor training in real world conditions. An advantage of immersive virtual reality that has not been fully leveraged is that it can introduce transient visual pertu...
Article
Full-text available
Virtual reality has been increasingly used in research on balance rehabilitation because it provides robust and novel sensory experiences in controlled environments. We studied 19 healthy young subjects performing a balance beam walking task in two virtual reality conditions and with unaltered view (15 minutes each) to determine if virtual reality...
Article
Full-text available
Background Controllers for assistive robotic devices can be divided into two main categories: controllers using neural signals and controllers using mechanically intrinsic signals. Both approaches are prevalent in research devices, but a direct comparison between the two could provide insight into their relative advantages and disadvantages. We stu...
Article
Full-text available
More neuroscience researchers are using scalp electroencephalography (EEG) to measure electrocortical dynamics during human locomotion and other types of movement. Motion artifacts corrupt the EEG and mask underlying neural signals of interest. The cause of motion artifacts in EEG is often attributed to electrode motion relative to the skin, but fe...
Article
Studying human and animal locomotion on uneven terrain can be beneficial to basic science and applied studies for clinical and robotic applications. Traditional biomechanical analysis of human locomotion has often been limited to laboratory environments with flat, smooth runways and treadmills. We modified a regular exercise treadmill by attaching...
Article
Full-text available
Background: Modules of muscle recruitment can be extracted from electromyography (EMG) during motions, such as walking, running, and swimming, to identify key features of muscle coordination. These features may provide insight into gait adaptation as a result of powered assistance. The aim of this study was to investigate the changes (module size,...
Article
Full-text available
This study aimed to determine if there are electrocortical evidence of augmented participation of sensory brain areas on walking modulation during walking with eyes closed. Healthy subjects (n=10) walked on a treadmill at 1 m/s while alternating 5 minutes walking with the eyes open or closed while we recorded ground reaction forces (GRF) and high-d...
Conference Paper
There are an infinite number of ways to control an assistive robotic device; however, there is little consensus on which ways are better than others and why. We designed this study to compare the control of powered ankle exoskeletons using neural measurements to drive control versus that using mechanically intrinsic measurements. The controller dri...
Article
Lower-limb assistive robotic devices are often evaluated by measuring a reduction in the user's energy cost. Using indirect calorimetry to estimate energy cost is poorly suited for real-time estimation and long-term collection. The goal of this study was to use data from wearable sensors to predict energy cost with better temporal resolution and le...
Article
Full-text available
Sensorimotor processing is a critical function of the human brain with multiple cortical areas specialised for sensory recognition or motor execution. Although there has been considerable research into sensorimotor control in humans, the steps between sensory recognition and motor execution are not fully understood. To provide insight into brain ar...
Article
Full-text available
Background Despite a large increase in robotic exoskeleton research, there are few studies that have examined human performance with different control strategies on the same exoskeleton device. Direct comparison studies are needed to determine how users respond to different types of control. The purpose of this study was to compare user performance...
Data
Demonstration of exoskeleton controllers.
Article
Full-text available
Mobile electroencephalography (EEG) is a very useful tool to investigate the physiological basis of cognition under real-world conditions. However, as we move experimentation into less-constrained environments, the influence of state changes increases. The influence of stress on cortical activity and cognition is an important example. Monitoring of...
Preprint
Full-text available
In a recently published study [1], we investigated how human pupil sizes are modulated by task experience as well as attentional load in a visuospatial task. In particular, participants performed a multiple object tracking (MOT) task while pupil sizes were recorded using binocular eyetracking measurements. To vary the attentional load, participants...
Article
Full-text available
Recording scalp electroencephalography (EEG) during human motion can introduce motion artifacts. Repetitive head movements can generate artifact patterns across scalp EEG sensors. There are many methods for identifying and rejecting bad channels and independent components from EEG datasets, but there is a lack of methods dedicated to evaluate speci...
Article
Full-text available
Lab-based electroencephalography (EEG) techniques have matured over decades of research and can produce high-quality scientific data. It is often assumed that the specific choice of EEG system has limited impact on the data and does not add variance to the results. However, many low cost and mobile EEG systems are now available, and there is some d...
Article
Full-text available
A broad goal in the field of powered lower limb exoskeletons is to reduce the metabolic cost of walking. Ankle exoskeletons have successfully achieved this goal by correctly timing a plantarflexor torque during late stance phase. Hip exoskeletons have the potential to assist with both flexion and extension during walking gait, but the optimal timin...
Article
Research on robotic exoskeletons has rapidly expanded over the previous decade. Advances in robotic hardware and energy supplies have enabled viable prototypes for human testing. This review paper describes current lower limb robotic exoskeletons, with specific regard to common trends in the field. The preponderance of published literature lacks ri...
Article
Full-text available
Robotic exoskeletons and bionic prostheses have moved from science fiction to science reality in the last decade. These robotic devices for assisting human movement are now technically feasible given recent advancements in robotic actuators, sensors, and computer processors. However, despite the ability to build robotic hardware that is wearable by...
Article
Full-text available
Previous studies have related changes in attentional load to pupil size modulations. However, studies relating changes in attentional load and task experience on a finer scale to pupil size modulations are scarce. Here, we investigated how these changes affect pupil sizes. To manipulate attentional load, participants covertly tracked between zero a...
Data
Figure of pupil size traces as a function of attentional load for each day condition. (TIFF)
Data
Zip file containing aggregated datasets underlying Figs 2, 3 and 4. (ZIP)
Data
Link to the raw MOT task performance and eyetracking data (osf.io/qtzjb). (PDF)
Article
New & noteworthy: We are presenting novel subject-specific metabolic cost landscape confidence analyses. These confidence analyses can greatly improve experimental design, intersubject analysis, and the comparison of landscape mapping protocols. We validated these methods by mapping subject-specific metabolic cost landscapes using bilateral ankle...
Conference Paper
Full-text available
In recent years there was a change in EEG experimental designs-from simple behavior in the lab to complex behavior outside. That change required also an adjustment of EEG systems – from being static and sensitive to mobile and noise-resistant. The rapid technological development has to balance performance (e.g. number of channels, low impedance con...
Article
Full-text available
Although there have been many lower limb robotic exoskeletons that have been tested for human walking, few devices have been tested for assisting running. It is possible that a pseudo-passive elastic exoskeleton could benefit human running without the addition of electrical motors due to the spring-like behavior of the human leg. We developed an el...
Article
Objective: Electroencephalography (EEG) can assess brain activity during whole-body motion in humans but head motion can induce artifacts that obfuscate electrocortical signals. Definitive solutions for removing motion artifact from EEG have yet to be found, so creating methods to assess signal processing routines for removing motion artifact are...
Article
Full-text available
Recent advances in electroencephalographic (EEG) acquisition allow for recordings using wet and dry sensors during whole-body motion. The large variety of commercially available EEG systems contrasts with the lack of established methods for objectively describing their performance during whole-body motion. Therefore, the aim of this study was to in...
Article
Full-text available
Active and viewed limb movement activate many similar neural pathways, however, to date most comparison studies have focused on subjects making small, discrete movements of the hands and feet. The purpose of this study was to determine if high-density electroencephalography (EEG) could detect differences in cortical activity and connectivity during...